A method and apparatus for switching connection in a wireless communication system is provided. A device receives a base station-to-device (B2D) switch request message or an unsolicited B2D switch response message from a base station. The B2D switch request message or the unsolicited B2D switch response message include information on at least one of a target device, a switch unit, target D2D connection/link identifier(s), an enhanced packet system (EPS) bearer identity, a data radio bearer (DRB) identity, a radio link control (RLC) configuration, a logical channel identity, and when to switch from a device-to-device (D2D) connection to a B2D connection.
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1. A method for switching from a device-to-device (D2D) connection to a base station-to-device (B2D) connection, by a first device, in a wireless communication system, the method comprising: transmitting first data traffic to a second device through the D2D connection, wherein the first device is in a radio resource control (RRC) idle state, wherein the second device is in a RRC connected state; receiving a B2D switch request message from a base station, wherein the B2D switch request message includes information on the second device, a switch unit, D2D connection/link identifier(s) of the second device, an enhanced packet system (EPS) bearer identity, a data radio bearer (DRB) identity, a radio link control (RLC) configuration, a logical channel identity, and a B2D switch time identifying when the first device is to switch from the D2D connection to a B2D connection; transmitting a B2D switch response message, to the base station, as a response to the B2D switch request message; releasing the D2D connection, wherein, according to the switch unit, the D2D connection is released per flow, per bearer, or for all flows; and transmitting second data traffic to the base station, which delivers the second data traffic to the second device.
A device switches from a direct device-to-device (D2D) connection with a second device to communicating with a base station to reach that same second device. The first device, initially in an idle state, transmits data to a second device that is in a connected state. The base station sends the first device a message containing information about the second device, a unit indicating how to switch connection, identifiers for the D2D link, identifiers for packet data and radio bearers, radio link configuration, a logical channel, and a specific time for switching from D2D to communicating through the base station. The first device responds to the base station, releases the direct D2D link (releasing either a specific data flow, a data bearer, or the entire D2D connection depending on the switch unit), and begins transmitting data to the base station, which then forwards the data to the original second device.
2. The method of claim 1 , further comprising: receiving a paging message from the base station; and performing an RRC connection establishment procedure with the base station.
In addition to the D2D-to-base station switching process, the first device receives a paging message from the base station and then establishes a radio resource control (RRC) connection with the base station. This involves procedures necessary to transition from an idle state to a connected state, ensuring reliable communication with the base station before switching from the direct D2D link, as described in the process of switching from a device-to-device (D2D) connection to a base station-to-device (B2D) connection, where the first device transmits data to a second device through the D2D connection while in an idle state and the second device is in a connected state, receiving a B2D switch request message from a base station, transmitting a B2D switch response message, releasing the D2D connection, and transmitting data to the base station for delivery to the second device.
3. The method of claim 1 , further comprising performing an RRC connection reconfiguration procedure with the base station.
In addition to the D2D-to-base station switching process, the first device also performs a radio resource control (RRC) connection reconfiguration procedure with the base station. This involves adjusting parameters of the radio connection, such as frequency, power, or data rates, as directed by the base station to optimize communication after switching from the direct D2D link, building upon the switching method from a device-to-device (D2D) connection to a base station-to-device (B2D) connection including transmitting data to a second device via D2D, receiving the switch request with device information, D2D link identifiers, radio bearer information, radio link configuration and switch time, transmitting a switch response, releasing the D2D connection, and then sending data to the base station for the second device.
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July 1, 2013
May 16, 2017
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